1. Field of the Invention
The present invention relates to an image processing device which processes an image for use at the time of diagnosis of atrophic gastritis, and an operation method therefor.
2. Description Related to the Prior Art
In a medical field, diagnosis or the like using an endoscope system comprising a light source device, an electronic endoscope, and a processor device has been widely performed. In a recent endoscope system, with high resolution using a high-vision system, such as high sensitivity or an increase in the number of pixels of an imaging element incorporated in an electronic endoscope, a high-definition image exceeding conventional image quality has been able to be displayed. With this, it is possible to depict even a small lesion of a fine blood vessel or a mucosa very realistically.
With the realization of high-vision, since the shape or size of a lesion part is made clear, it is possible to facilitate the detection of the lesion part. However, a doctor finds the lesion part from a slight difference in color of a mucosa as well as the shape or size of the lesion part. For example, a portion which is reddish and has a slight difference in color from the mucosa is detected as an early lesion part. There is a case where the slightly reddish portion cannot be found even if high-vision is realized if just resolution is increased.
Accordingly, in Japanese Patent No. 3228627, color enhancement processing for reddening a reddish portion and whitening a white portion is performed to make a boundary of a lesion part noticeable. As in United States Patent Application Publication No. 2012/0078044 (corresponding to JP2012-71012A), the size of a discolored area different in color from a mucosa, such as a brownish area (BA), is detected, and frequency band-enhancement processing is performed according to the size of the discolored area to enhance the structure of the discolored area. The color enhancement processing or frequency band enhancement processing is performed, whereby it is possible to find a lesion part which cannot be found with just the realization of high-vision.
In recent years, a lesion part of the stomach, such as a gastric cancer, has been detected from the state of atrophic gastritis. This uses the following relationship between atrophic gastritis and the lesion part of the stomach. In a case of a normal gastric mucosal structure shown in FIG. 18A, since a mucosal layer of a surface is increased in thickness, most of light is absorbed or reflected in the mucosal layer. For this reason, as shown in FIG. 18B, it In contrast, as shown in FIG. 19A, in a case of a gastric mucosal structure in which atrophic gastritis has progressed, a mucosal layer is decreased in thickness with a decrease in the number of gastric gland cells. The change of the internal structure of the gastric mucosa with the progress of atrophic gastritis appears as changes (A) and (B) described below on an endoscopic image.
(A) A lamina muscularis mucosae of a color close to white becomes see-through, and the color of atrophic mucosa becomes a faded color compared to a normal part.
(B) In an area where there is an atrophic mucosa, when a mucosal layer is decreased in thickness with atrophy, a blood vessel of a submucosa becomes see-through (see FIG. 19B).
Accordingly, in diagnosis of a gastric lesion part based on atrophic gastritis, the degree of progress of atrophy or the boundary between a normal part and a gastritis part is determined using the two features (A) and (B) described above.
In a case where atrophy has progressed to a high degree (for example, in a case of atrophy included in a group C or a group Din an ABC examination), it is possible to observe the two features (A) and (B) described above on an endoscopic image clearly. However, in a case where atrophy has not progressed much, that is, atrophy is progressing (for example, in a case of atrophy included in a group B or a group C in an ABC examination), the difference between an atrophic part and a normal part on an endoscopic image is slight, and it is difficult to determine the degree of progress of atrophy or the boundary between a normal part and a gastritis part in some cases. Accordingly, there is a demand for making the two features (A) and (B) described above on an endoscopic image clear to make the boundary between a normal part and a gastritis part clear.
In regard to this, the application of the methods of Japanese Patent No. 3228627 and United States Patent Application Publication No. 2012/0078044 is considered. The method of Japanese Patent No. 3228627 enhances a color such that a reddish portion becomes redder, instead of enhancing change in color faded with atrophy of the stomach or change in color such that a blood vessel of a submucosa becomes see-through with atrophy of the stomach. The method of United States Patent Application Publication No. 2012/0078044 performs enhancement processing of a frequency band according to the size of the discolored area, instead of performing enhancement processing according to change in color with atrophy of the stomach.